1. Field of the Invention
The present invention relates to an image processing device, an image processing method and an image processing program. Particularly, the invention relates to an image processing device, an image processing method and an image processing program for producing an image of a high resolution by joining a plurality of images obtained from divided portions of a subject.
2. Description of the Related Art
Such a technique has been known that can obtain an image of high resolution by joining a plurality of partial images obtained from divided portions of a subject. This is an effective technique for obtaining high-resolution images in the case where a resolution of an acquirable image is restricted due to the number of pixels of a charge coupled device (which will be referred to as a “CCD” hereinafter) or the like. This technique is disclosed, e.g., in Japanese Patent Laying-Open Nos. 6-164890, 5-12430 and 6-98101.
In the joining techniques disclosed therein, characteristic points and a correlation in change of pixel values are detected, and positioning or registration is performed based on the relative positional relationship between the images thus obtained.
In the conventional joining technique, however, regions of the partial images to be joined may not accurately overlap with each other due to shift in position occurred at the time of taking partial images by the CCD or the like, distortions in lens, affine strain or the like. In this case, unnatural images or blurred images are formed in a joint or border between joined images, resulting in low image quality.
Such a problem also arises that long times are required for detecting corresponding characteristic points in the divided images to be joined and detecting the correlation in change of the pixel values.